Solid state synthesis of Li2Co0.5Cu0.5Ti3O8 and Li2CoTi3O8 and their comparative lithium storage properties

Abstract Li 2 MTi 3 O 8 (M=Co, Co 0.5 Cu 0.5 ) spinels were successfully synthesized by a simple high temperature solid-state method. Both Li 2 CoTi 3 O 8 and Li 2 Co 0.5 Cu 0.5 Ti 3 O 8 show a cubic structure with P4 3 32 space group. Rietveld refinement result reveals that Li 2 CoTi 3 O 8 can be described as [Li 0.5 Co 0.45 ] tet [(Li 0.5 Co 0.05 )Ti 1.5 ] oct O 4 . After Cu 2+ doping, half Co 2+ in [Li 0.5 Co 0.45 ] tet [(Li 0.5 Co 0.05 )Ti 1.5 ] oct O 4 is replaced by Cu 2+ to form a complex spinel titanate [Li 0.5 Co 0.225 Cu 0.225 ] tet [(Li 0.5 Co 0.025 Cu 0.025 )Ti 1.5 ] oct O 4 without structural changes. As lithium storage material, Li 2 CoTi 3 O 8 shows poor electrochemical performance at a current density of 100 mA g −1 in the potential window of 0.0–3.0 V. After 50 cycles, Li 2 CoTi 3 O 8 maintains a reversible capacity of 42 mAh g −1 with a low capacity retention of 19.5%. For comparison, Li 2 Co 0.5 Cu 0.5 Ti 3 O 8 can deliver a higher reversible capacity of 98 mAh g −1 after 50 cycles with a capacity retention of 44.4%. It suggests that copper ion doing can effectively enhance the capability for electrochemical lithium storage in Li 2 CoTi 3 O 8 .